This invention relates in general to driveshaft assemblies, such as those commonly found in the drive train systems of most vehicles. In particular, this invention relates to an improved seal arrangement for use with a slip joint in such a driveshaft assembly.
Drive train systems are widely used for generating power from a source and for transferring such power from the source to a driven mechanism. Frequently, the source generates rotational power, and such rotational power is transferred from the source to a rotatably driven mechanism. For example, in most land vehicles in use today, an engine/transmission assembly generates rotational power, and such rotational power is transferred from an output shaft of the engine/transmission assembly through a driveshaft assembly to an input shaft of an axle assembly so as to rotatably drive the wheels of the vehicle. To accomplish this, a typical driveshaft assembly includes a hollow cylindrical driveshaft tube having a pair of end fittings, such as a pair of tube yokes, secured to the front and rear ends thereof. The front end fitting forms a portion of a front universal joint that connects the output shaft of the engine/transmission assembly to the front end of the driveshaft tube. Similarly, the rear end fitting forms a portion of a rear universal joint that connects the rear end of the driveshaft tube to the input shaft of the axle assembly. The front and rear universal joints provide a rotational driving connection from the output shaft of the engine/transmission assembly through the driveshaft tube to the input shaft of the axle assembly, while accommodating a limited amount of angular misalignment between the rotational axes of these three shafts.
Not only must a typical drive train system accommodate a limited amount of angular misalignment between the source of rotational power and the rotatably driven device, but it must also typically accommodate a limited amount of relative axial movement therebetween. For example, in most vehicles, a small amount of relative axial movement frequently occurs between the engine/transmission assembly and the axle assembly when the vehicle is operated. To address this, it is known to provide a slip joint in the driveshaft assembly. A typical slip joint includes first and second members that have respective structures formed thereon that cooperate with one another for concurrent rotational movement, while permitting a limited amount of axial movement to occur therebetween. Two types of slip joints are commonly used in conventional driveshaft assemblies, namely, a sliding spline type and a rolling ball spline type.
A typical sliding spline type of slip joint includes male and female members having respective pluralities of splines formed thereon. The male member is generally cylindrical in shape and has a plurality of outwardly extending splines formed on the outer surface thereof. The male member may be formed integrally with or secured to an end of the driveshaft assembly described above. The female member, on the other hand, is generally hollow and cylindrical in shape and has a plurality of inwardly extending splines formed on the inner surface thereof. The female member may be formed integrally with or secured to a yoke that forms a portion of one of the universal joints described above. To assemble the slip joint, the male member is inserted within the female member such that the outwardly extending splines of the male member cooperate with the inwardly extending splines of the female member. As a result, the male and female members are connected together for concurrent rotational movement. However, the outwardly extending splines of the male member can slide relative to the inwardly extending splines of the female member to allow a limited amount of relative axial movement to occur between the engine/transmission assembly and the axle assembly of the drive train system.
Typically, the driveshaft assembly is located on the underside of the vehicle where contaminants, such as dirt, water, and the like, could enter the assembly at the slip joint if it were not adequately sealed. The area on the surface of a driveshaft assembly, where the sleeve shaft terminates and ceases to overlap the outer surface of the inner shaft, is highly susceptible to the entrance of contaminants, which can interfere with axial movement of the sleeve shaft relative to the inner shaft. These contaminants can also cause corrosion and rust on the components of the driveshaft assembly. To avoid this difficulty and to seal the slip joint, it is conventional practice to use a boot fixed at each of its ends, one end being secured to the outer surface of the outer shaft, the other end of the boot being secured to the outer surface of the sleeve shaft. These boots are typically made of rubber and have folded or pleated surfaces that accommodate axial displacement of the two shafts and permit a minor amount of angular movement. However, these boots are relatively expensive and are themselves susceptible to wear and damage. Booted seals are also susceptible to damage due to the high temperature environment in which they operate. It is preferable to provide a reliable, movement-tolerant seal against the entrance of contaminants, a seal that can endure a high temperature environment and is not susceptible to damage, such as the splitting and tearing that may occur with a booted seal.